1. Field of the Invention
The present invention relates generally to an inkjet printer and to a cleaning device and method for cleaning the print head in an inkjet printer. The invention relates more particularly to a cleaning device and method for minimizing ink waste in an inkjet printer from cleaning processes executed in response to an operator command.
2. Description of Related Art
Inkjet printers print text and images on a print medium by discharging ink from the ink nozzles of a print head. Water is typically used as the ink solvent, and if ink is not discharged from the ink nozzles for a certain period of time, the water evaporates and the viscosity of the ink left in the nozzles increases. As a result, the nozzles clog, ink is not discharged or is not discharged at the normal size and speed, resulting in printing defects (referred to below as dropped dots). To prevent this, inkjet printers cover the nozzles with a cap when the print head is retracted to a standby position in order to prevent an increase in the viscosity of the ink in the nozzles.
However, simply covering the print head with a cap will not completely prevent the ink in the nozzles from increasing in viscosity when nothing is printed for an extended period of time. Depending on how the print head is used, dropped dots may also result from the ink meniscus inside the nozzles breaking during printing, such as when printing continues uninterrupted for a long time and the print head is repeatedly driven bidirectionally.
Inkjet printers therefore have a cleaning device for forcibly removing high viscosity ink inside the nozzles and restoring the ink meniscus. The cleaning device may drive an ink suction pump connected to the cap to vacuum ink for a predetermined time from all of the nozzles in a vacuum process, or discharge a very small amount of ink from all of the nozzles in a flushing process, or wipe the nozzle surface of the print head with a flexible blade in a wiping process, for example.
The vacuum process expels high viscosity ink and air bubbles from the nozzles (inside the ink path) and supplies new ink to the nozzles, and therefore effectively restores clogged nozzles. The flushing process effectively restores the ink meniscus, and wiping processes effectively remove contamination such as paper and ink waste adhering to the nozzle surface.
JP-A-2003-89226 teaches an inkjet printer that detects the nozzle condition, that is, whether the nozzles are clogged or whether ink is on the nozzle surface around the nozzles, and automatically executes the appropriate cleaning process according to the condition of the nozzles.
Other inkjet printers known from the literature automatically execute the appropriate cleaning process based on historical information, such as how much time has passed since the last cleaning process.
The vacuum process consumes a large amount of ink, and if the vacuum process is executed frequently by the automatic cleaning process, ink consumption rises accordingly and the cost of printing therefore rises. Conventional inkjet printers therefore set low frequency at which the vacuum process is executed by the automatic cleaning process, and provide a cleaning button enabling the operator to manually apply a cleaning process, including the vacuum process, if dots are dropped because the vacuum process has not been applied.
Many operators of inkjet printers that have a cleaning button and are unaccustomed to the printer often mistakenly operate the cleaning button when turning the printer power on, resulting in the vacuum process being frequently applied, thus increasing ink waste and increasing the cost of printing. This also increases the operating time of the ink vacuum pump, and can thus also shorten the service of the vacuum pump and other parts.